As baby boomers age, 13.8 million are expected to have Alzheimer's disease by 2050, a study finds. Experts say caring for all those patients may cost $1 trillion a year.

As baby boomers enter their golden years, the number of people afflicted with Alzheimer's disease is expected to reach 13.8 million by 2050 — millions more than previously anticipated, according to a new study in the journal Neurology.

If researchers can't find a way to reduce the prevalence of the brain disease, the cost to care for all of these patients could top $1 trillion a year, experts say.

Alzheimer's is a progressive brain disease that damages patients' memory and cognitive skills, ultimately leaving them unable to care for themselves. Scientists aren't sure how it starts, but they believe it causes plaques and tangles to form in the brain, slowly killing neurons and causing the entire brain to shrink. Between 60% and 80% of dementia cases are believed to be a consequence of Alzheimer's, according to the Alzheimer's Assn.

The risk of developing the disease rises with age. So while deaths from breast and prostate cancer, heart disease, stroke and HIV all fell between 2000 and 2008, the number of Alzheimer's-related deaths grew by two-thirds in the same period — a macabre result of people living longer than ever before.

Doctors, researchers and public health experts are already bracing for an onslaught of new patients by developing drugs and preparing caregivers for the emotional and physical stress.

"This is an issue that's going to touch each of us personally or someone that we know and care about," said Lora Connolly, director of the California Department of Aging, which expects to be serving as many as 1.2 million patients with Alzheimer's or dementia in the state by 2030. "It won't happen overnight, but the pressure will continue to mount."

The new projections released Wednesday are based on a study of 1,913 senior citizens from the Chicago area who were evaluated for Alzheimer's between 1997 and 2011.

Researchers from the Rush Institute for Healthy Aging in Chicago evaluated the study volunteers every three years, conducting in-home interviews and clinical checkups to see whether they were developing symptoms of dementia. Participants were all at least 65 years old and came from a variety of ethnic, socioeconomic and education backgrounds.

A total of 402 people were newly identified with Alzheimer's during the study period, and as expected, the incidence increased with age.

The researchers used models to extrapolate their results to the entire U.S. population and make projections for the year 2050. They calculated that 1.3 million people between the ages of 65 and 74 would have Alzheimer's, along with 5.4 million 75- to 84-year-olds and 7 million people who had passed their 85th birthday. The grand total was 13.8 million patients.

Put another way, the researchers projected that 3.3% of 65- to 74-year-olds, 18.5% of 74- to 84-year-olds and 36.6% of those 85 and older would have Alzheimer's by the midpoint of the century.

The Alzheimer's Assn. estimates that it costs $200 billion a year to care for today's Alzheimer's patients, with $140 billion of that paid by Medicare and Medicaid. By 2050, that bill will swell to more than $1 trillion a year, the group says.

The growth in new cases — especially as baby boomers pass the age of 75 — will put pressure on generations behind them to provide massive amounts of care.

Baby boomers have "had a major impact on every system since they've been born," said Maria Carrillo, a scientist with the Alzheimer's Assn. in Chicago.

The federal government responded to the looming crisis in 2011 by starting the National Alzheimer's Project, which brings together public, private and nonprofit organizations to develop a plan to treat Alzheimer's patients and help their caretakers in the decades to come.

One of the project's goals is to have drugs available to treat Alzheimer's by 2025. Current research is focused on identifying early symptoms of the disease so that patients could begin therapies to slow or halt its progression.

"In the next five or six years, we'll have some indication whether this strategy with these particular kinds of drugs works," said Neil Buckholtz, director of the National Institute on Aging's Division of Neuroscience.

Federal funding for Alzheimer's research increased from $450 million in 2011 to $500 million last year. The Obama administration is asking for an additional $30 million in 2013.

The Neurology study was provided by the Alzheimer's Assn. and the National Institute on Aging, which is part of the National Institutes of Health.